Late blight on potatoes: description and control methods

A disease such as late blight or brown rot is a common occurrence in summer cottages. This disease typically appears mid-season and can destroy all nightshade crops. To avoid infestation, some gardeners try to grow early-ripening fruits to clear the area before the blight becomes active. Others spray their plants with various solutions daily, hoping that the brown rot will pass them by.

Unfortunately, planting nightshade vegetables ahead of schedule and avoiding late blight is only possible in the south, and only if the soil temperature has reached the desired level by then. In northern cities, sowing seedlings outdoors may have to be postponed, as the weather in temperate climates is unpredictable, requiring careful planting to avoid damaging the seedlings. Therefore, it's likely that harvesting dates will also be delayed slightly, meaning late blight will already be devastating the plants.

While tomatoes and other above-ground vegetables can be harvested early and stored in a dark place until ripening, this trick won't work with potatoes, which can quickly die. To prevent this, let's learn more about our enemy, late blight, and find out how to combat it without harming your potato tubers.

Symptoms of late blight

If you closely monitor the appearance of your potato tops, you can easily detect late blight. Initially, green leaves are affected by brown rot. A dark, dirty-gray spot develops rapidly, covering the entire leaf. The affected areas quickly dry out and begin to fall off. Upon closer inspection, you may notice a web-like white formation on the lower edge of the leaf, resembling a plaque. This plaque is where fungal infections actively develop.

If the infection isn't prevented promptly, late blight will continue to negatively impact the potato, destroying the stem. Soon, the infection will spread to the tubers. Gray spots first appear on the skin, then brown rot attacks the fruit from the inside. The potato flesh turns black and begins to decompose. When cut, rusty necrosis can be seen, which quickly spreads throughout the entire potato.

Causes of brown rot

Late blight spores can appear on a plot for various reasons. The most common are contaminated plant debris or the airborne spread of the disease from a neighboring garden. There have been cases where late blight spores were introduced into the soil by adding new soil. However, brown rot does not activate without favorable conditions, which may include:

• High humidity. Several years ago, it was discovered that late blight spores are killed by high temperatures or exposure to direct sunlight. Therefore, it is crucial to water the plants at the roots, avoiding moisture getting on the tops.
• Weakened plants. It's not surprising that when choosing seedlings, it's best to choose strong, healthy plants, as weak and stunted seedlings are more susceptible to various diseases due to a weakened immune system. Early mineral fertilizers and natural hardening of the planting material can help improve the situation.
• Dense plantings. Each vegetable has its own planting distance in open ground. Failure to follow this basic rule leads to plants being too close together, which leads to faster bacterial spore development in such dense plantings. To prevent this, maintain a certain distance between plants and thin them out more frequently if planting too closely.

Even if you follow all the above recommendations, late blight can still occur in your garden. Nature itself can create ideal conditions for brown rot to develop. After all, a rainy and cool summer is the best time for late blight. To get rid of this disease, you can use special treatments.

How to combat late blight

This dangerous disease can spread to other vegetables if the source of the fire isn't contained promptly. Many remedies are effective in combating late blight, but we'll share the most effective ones.

Folk remedies

Chemical treatments are much more effective against fungal diseases, but they are expensive, and some products simply cannot be used during the flowering period. Therefore, during the flowering and development period of potatoes, it's better to use the methods our ancestors used.

• Infusion of garlic and potassium permanganate.

The excellent combination of garlic aroma and antibacterial properties will protect plants from fungus for a long time. To prepare the desired mixture, simply pour 100 g of crushed garlic into a glass of warm water. Let the infusion steep for 24 hours, then strain through a sieve. Pour the garlic infusion into a bucket with 10 liters of water and add 1 g of potassium permanganate. Mix thoroughly and water the plants. Half a liter of liquid is enough for one plant.

• Milk whey.

Dilute the fermented milk product with settled water in a 1:1 ratio and spray it on the potato tops. For best results, it is recommended to repeat the procedure twice a week.

• Ash.

An excellent remedy that not only eliminates various diseases but also prevents larvae. A week after planting the potato seed, dust the top layer with ash powder. Repeat the dusting after a couple of weeks.

• Yeast.

Diseased bushes can be treated with regular yeast: a 100g package should be diluted in 10 liters of water. At the first signs of late blight, water the bushes with the resulting solution. Repeat the spraying after two weeks, if necessary.

• Horsetail.

Horsetail is an effective remedy against brown rot. Add 100 g of the dry mixture to a liter of water, simmer over medium heat for half an hour, and dilute with 5 liters of settled water. Spray potato tops twice a month.

Furgicidal drugs

Furgicides are a class of chemicals known as pesticides. These products are designed to prevent and treat fungal diseases. Furgicides are divided into several groups, each responsible for a specific effect on plants, such as:

• Protective. The main purpose of protective preparations is to prevent the growth of fungi and spores on the plant;
• medicinal furgincides treat already diseased plants;
• systemic – absorbed into plants, providing a protective effect from the inside;
• Contact. They have only a protective effect and are easily washed off with water;
• Seed treatments are used before sowing, treating the planting material in liquid to protect the plant and increase the immune system of the roots.

List of the most popular drugs.

• Topaz.

This is a systemic furniticide. Treatment of plants during flowering is prohibited. The chemical is dangerous to animals and humans, so only the tops are treated. Avoid contact with the fruit. Before eating vegetables, it is recommended to rinse thoroughly under running water.

• Fitosporin-M.

This biofungicide has a protective effect on plants. It is low in toxicity and is used to treat planting material. It is mainly sold as a paste.

• HOM.

The product combats diseases, so it is used to treat already infected bushes. Avoid letting HOM enter water bodies, as it is harmful to fish and other aquatic life. The last spraying with this solution should occur three weeks before harvest.

• Copper sulfate.

The main purpose of this product is to disinfect wounds and combat brown rot. Dilute 50-100 g of this product in 10 liters of water, stir the resulting solution until the crystals dissolve, and spray on plants.

• Bordeaux mixture.

Bordeaux mixture, which contains copper and lime, does a good job of protecting potatoes. However, preparing this solution for watering plants isn't easy. The slightest mistake can alter the structure, ruining the potatoes.

First, dissolve copper sulfate in warm water. Then add cool liquid to make a total of 5 liters of solution. In another container, dissolve lime in a liter of water, then add liquid to make a total of 5 liters. Strain the limewater through a sieve. Carefully pour the copper sulfate solution into the limewater, stirring constantly with a wooden stick. Use the solution immediately as directed.

Trichopolum

This product is a godsend for gardeners. Trichopolum, whose active ingredient is metronidazole, is harmless to fruits and the human body. It is most often sold as tablets, which must be dissolved in a small amount of warm water, then topped up with about 10 liters of clear liquid. After preparing the solution, spray the bushes.

Preventive measures

Late blight can appear suddenly on potato plants. To prevent this, it is necessary to take a number of preventative measures that will protect the tubers and tops from brown rot.

1. In addition to the main factors, the choice of planting site also influences the development of fungal diseases. When planting potatoes, it's important to choose a site that is free from shade and moisture.
2. Crop rotation plays a significant role, as late blight primarily affects nightshade crops. Therefore, planting potato roots in place of tomatoes, eggplants, and other nightshade vegetables is strictly prohibited.
3. Selecting healthy planting material and warming it up will eliminate spores in the tubers and ensure a good yield.
4. Applying potassium fertilizers at an early stage of plant development will protect crops from brown rot.
5. Hilling seedlings has a beneficial effect on the sprouts and protects them from diseases.
6. If forecasters predict prolonged rains at the end of the summer cottage season, it's best to dig up the harvest and store it in a dry, dark place to ripen.
7. After harvesting, it is important to dig up all weeds and remove any remaining debris from the area that could serve as a source of infection for the following year.

By taking a number of preventative measures, your seedlings will be under reliable protection.

Potato varieties resistant to late blight

To reap a bountiful potato harvest and avoid the risk of late blight, we recommend planting only proven potato varieties in your garden. These varieties have strong immunity and are resistant to brown rot. Here's a list of the most popular potato varieties.

• Spring.

This potato with an unusual name is an early-ripening variety. Its high yield and resistance to many diseases make it a top-selling variety. The oval-shaped fruit with light pink skin appeals to many gardeners. When cut, the vegetable has white flesh. This potato withstands any kitchen challenge and makes a wonderful addition to dishes.

• Blue.

Why the variety was named "Golubizna" is probably only known to the breeders. After all, the potato has round tubers with light-brown skin. The white flesh remains intact even after cooking. This vegetable makes delicious mashed potatoes and excellent homemade chips.

• Nevsky.

The delicate flavor of the round white tubers, covered in white-yellow skin, has been in great demand among gardeners for many years. The variety is resistant to many diseases and pests. The good shelf life of the fruit allows for a harvest to be stored for future use.

• Red Scarlett

Smooth, pink, oval-shaped roots with excellent flavor offer a number of advantages. This variety stores well for a long time, and its appearance remains unchanged even after long storage. Red Scarlett is used in a variety of culinary applications.

• Luck.

This early-ripening variety produces round fruits with light skin and yellowish flesh. Its high yield and excellent shelf life are appreciated by many gardeners, making this "Udacha" variety a popular choice in garden plots.

Any of the above varieties is suitable for growing potatoes in different regions of the country. Each type has a high degree of resistance to late blight; however, without preventative measures, even these varieties can be susceptible to brown rot. Therefore, carefully monitor the planted plants to prevent foliar infection.

Rules for storing potatoes

Proper storage of potatoes after harvest is crucial, including shelf life. To prevent them from spoiling prematurely, we recommend following these tips.

• Dark room.

Darkness plays a crucial role in storing potatoes. Without light, the tubers will begin to sprout, meaning the harvest won't last long and will soon begin to spoil. A cellar or basement is the optimal location for storing potatoes.

• Temperature conditions.

The ideal room temperature is 2-3 degrees Celsius. At this temperature, the fruits will not sprout or spoil.

• Dryness.

The room where the potatoes will be stored must be dry, otherwise it will become a breeding ground for spores and viruses. Incidentally, potato tubers should be stored dry.

• Storage container.

Wooden or plastic boxes can be used as "containers." They're convenient for storing potatoes and make it easier to spot damaged ones.

Frequently asked questions from new gardeners

Those growing potatoes for the first time often have a number of questions, the answers to which can be difficult to find. We decided to save you precious time and answer the questions that are sure to arise in the future.

How to treat for late blight during flowering

As mentioned earlier, not all methods are permitted during potato flowering. In addition to folk remedies, you can also use the following:

• Arcedil (50 g per 10 l of water);
• Ridomil MC (25 g per 10 l of water);
• Oxychom (20 g per 10 l of water).

Each solution can be used during the flowering period. It is recommended to water the plants once the stems reach 15-20 cm in height. As a preventative measure, treat the tops twice a month.

How to treat potatoes after flowering

At the end of the potato crop flowering period, it is recommended to replace the previous solutions with the following:

• Ditamine M-45 (20 g per 10 liters of water);
• Copper oxychloride (40 g per 10 l of water);
• Kuproxat (25 g per 10 liters of water).

Water the plant twice a month; three weeks before harvesting, stop spraying the potato foliage with chemicals and folk remedies.

How to treat potatoes in July

An effective method for combating late blight is a solution of copper sulfate, manganese, and boric acid. To prepare this powerful mixture, mix a teaspoon of each component in 10 liters of water and stir until the crystals are completely dissolved. Then spray the potatoes with the resulting solution and enjoy the results.

Please note that this mixture can only be used once per summer season, and this type of potato treatment is usually carried out in July.

Conclusion

To prevent brown rot from catching you off guard, we recommend spraying your planting material early as a preventative measure and closely monitoring the appearance of the leaves. If brown spots appear, immediately use other treatments to help extinguish the fire and save the harvest.

It is also worth remembering that pre-sowing treatment of tubers strengthens the immune system of seedlings and is able to resist various diseases.